The purpose of a defroster system in a motor vehicle is to prevent fogging and icing on the windshield at low ambient temperature, an objective which puts high demands on the system when severe frost conditions prevail. The typical defroster system is arranged such that the hot air current impinges against the windshield at the region somewhat below the portion of the windshield through which the vehicle operator is viewing to rapidly clear same of any fog and frost accumulation. Nevertheless, at extremely low ambient temperatures, any snow that is accumulating and freezing at the lower portion of the windshield may not all be melted. This is particularly undesirable for the reason that the windshield wiper blades are located in this area and, as a result, may be subjected to obstruction thereby.
The problem of ice accumulation on the lower portion of the windshield surface area, and obstruction thereby to the windshield wipers is more pronounced when the wipers are arranged so as to park below the rear edge of the engine hood, because with this arrangement the windshield must also be made to extend more downwardly than is otherwise required.
In an effort to overcome the aforementioned problems some remedies have been proposed in the past which, however, have proved to be relatively costly and complex. For instance, in accordance with the teaching contained in the German publication DE-OS-31 32 431, a surface area heat exchanger is arranged on the inner side of the windshield which is connected to the engine cooling system. In the German publication DE-OS-29 02 748 it has been proposed to provide an electrical resistance heater in the lower portion of the windshield where the windshield wipers are parked. Finally, the German publication DE-PS-941 891 describes a motor vehicle in which a hot air stream, which is coming from the engine compartment, is traveling outside the car from the lowermost edge of the windshield upwardly along the windshield.